The present invention pertains to field emission devices and, more particularly, to field emission devices having a surface passivation layer.
Field emission devices (FED""s) are known in the art. In a field emission device, electrons are emitted from a cathode and strike an anode liberating gaseous species. Emitted electrons also tend to strike gaseous species already present in the FED and form positively charged ions. The ions within the FED are repelled from the high positive potential of the anode and are caused to strike portions of the cathode. Those positive ions striking the dielectric layer portion of the cathode can be retained therein, resulting in a build up of positive potential. The build up of positive potential continues until either the dielectric layer breaks down due to the realization of the breakdown potential of the dielectric material, or until the positive potential is high enough to deflect electrons toward, and cause them to strike the dielectric layer. Ions can also strike electron emitters within the FED causing emitter damage and degrading FED performance.
Impinging ions can also liberate trapped gases within the dielectric layer and release oxygen due to chemical dissociation of the dielectric layer. Also, impinging ions can combine with elements within the dielectric layer to create additional gases, thereafter releasing them into the FED. Additionally, impinging ions can strike metal electrodes and liberate gases from the oxide coating the metal electrode thereby releasing gases into the FED. Other surfaces within the FED are potential sources of gas due to impinging electrons as well.
Accordingly, there exists a need for a field emission device having a structure and method that protects exposed dielectric surfaces within the device from electron and ion bombardment, prevents the liberation of trapped gases within the dielectric layer and traps bombarding ions within the device.